Device and method for supplying a reference audio signal to an acoustic processing unit

ABSTRACT

Equipment includes a first interface intended to be connected to a sound reproduction device and at least one second interface intended to be connected to at least one microphone, an acoustic processing unit adapted for delivering an audio signal filtered by attenuation or suppression of a reference audio signal from an audio signal received via the second interface. In an initialisation phase, the equipment determines a propagation latency; configures a buffer with a reading-triggering threshold defined according to the determined propagation latency. In a nominal operating phase, the equipment transmits a third audio signal via the first interface, the third audio signal being the reference signal after passing through the buffer.

The present invention relates to equipment comprising a first interfaceintended to be connected to a sound reproduction device and at least onesecond interface intended to be connected to at least one microphone,said equipment comprising an acoustic processing unit adapted fordelivering an audio signal filtered by attenuation or suppression of areference audio signal from an audio signal received via said secondinterface.

At the present time one can find numerous applications for voicerecognition thus controlling equipment by voice. The difficulty lies inbeing able to distinguish these voice commands from a noisy environment.

The same type of problem is found in the teleconferencing world. It maysometimes be difficult to clearly distinguish the words of a speakerbecause of a noisy environment.

This noisy environment is often related to an audio or audiovisualcontent that is reproduced during the teleconference or while the useris transmitting his voice command. Let's take for example the case of ahome-theatre system that one would wish to control by voice. When thehome-theatre system is operating, an audible signal is reproduced in theroom, potentially with a high sound volume. It would then be difficultfor the system to distinguish voice commands in this situation.

There exist components for suppressing a reference audio signal using anaudio signal captured thanks to one or more microphones. Electronicevaluation boards are available on the shelf on the basis of suchcomponents. However, these components and electronic evaluation boardsdo not enable obtaining a satisfactory result in many installationconfigurations. This is because, if the example is taken of theaforementioned home-theatre system, the propagation time in air ofaudible signals issuing from loudspeakers are dependent on the actuallocation of these loudspeakers and the configuration of these componentsand electronic boards is often unsuitable, which means that thecomponent does not find the reference signal in the audio signalcaptured by the microphone.

It is therefore desirable to overcome these drawbacks of the prior art.

The invention concerns equipment comprising a first interface intendedto be connected to a sound reproduction device and at least one secondinterface intended to be connected to at least one microphone, saidequipment comprising an acoustic processing unit adapted for deliveringan audio signal filtered by attenuation or suppression of a referenceaudio signal from an audio signal received via said second interface.The equipment is such that it comprises means for implementing aninitialisation phase, comprising: means for determining a propagationlatency between an instant of transmission of a first audio signal viasaid first interface and an instant of reception of a second audiosignal via said second interface; means for configuring a buffer with areading-triggering threshold defined according to said determinedpropagation latency. The equipment is such that it further comprisesmeans for implementing a nominal operating phase, comprising: means fortransmitting a third audio signal via said first interface, said thirdaudio signal being the reference signal after passing through saidbuffer.

Thus it is possible to perfectly adapt the configuration of theequipment to various situations in which the voice of a user must bedistinguished in a noisy or even very noisy environment because of anaudio signal that the equipment sends to the reproduction device.

According to a particular embodiment, said first audio signal consistsof a predefined pattern.

According to a particular embodiment, said means for determining thepropagation latency comprise means for detecting the crossing of anamplitude threshold of said second audio signal.

According to a particular embodiment, said means for determining thepropagation latency comprise a North filter applied between said firstaudio signal and said second audio signal.

According to a particular embodiment, said means for implementing theinitialisation phase are implemented in a control unit connected to anoutput of the acoustic processing unit so as to receive said filteredaudio signal, and the control unit deactivates any transmission of areference audio signal to said acoustic processing unit during saidinitialisation phase.

According to a particular embodiment, said means for implementing theinitialisation phase, said first interface and said means fortransmitting the third audio signal are implemented in a first device,and the acoustic processing unit and said second interface areimplemented in a second device intended to be connected to said firstdevice.

According to a particular embodiment, said microphone(s) beingunidirectional, the acoustic processing unit and said microphone(s) areimplemented in a box comprising, for each microphone, a first slot and asecond slot, and each microphone is installed in a cavity of a supportin which a first slot and a second slot are also formed, and placed soas to correspond respectively to said slots in the box when said supportis mounted in said box, said support being adapted so that the distancesbetween said first slots and a face of said microphone placed in thedirection of an audible signal to be favoured and the distances betweensaid second slots and a face opposite said microphone are substantiallyidentical.

The invention also relates to a method implemented by equipmentcomprising a first interface intended to be connected to a soundreproduction device and at least one second interface intended to beconnected to at least one microphone, said equipment comprising anacoustic processing unit adapted for delivering an audio signal filteredby attenuation or suppression of a reference audio signal from an audiosignal received via said second interface. The method is such that itcomprises an initialisation phase comprising the following steps:determining a propagation latency between an instant of transmission ofa first audio signal via said first interface and an instant ofreception of a second audio signal via said second interface;configuring a buffer with a reading-triggering threshold definedaccording to said determined propagation latency. The method is suchthat it further comprises a nominal operating phase comprising thefollowing step: transmitting a third audio signal via said firstinterface, said third audio signal being said reference signal afterpassing through said buffer.

The invention also concerns a computer program, which may be stored on amedium and/or downloaded from a communications network, so as to be readby a processor. This computer program comprises instructions forimplementing any of the methods mentioned above, when said program isexecuted by the processor. The invention also relates to storage meanscomprising such a computer program.

The features of the invention mentioned above, as well as others, willemerge more clearly from a reading of the following description of anexample embodiment, said description being given in relation to theaccompanying drawings, among which:

FIG. 1 schematically illustrates a system in which the invention may beimplemented;

FIG. 2A schematically illustrates an example of hardware architecture ofa source device of the system of FIG. 1;

FIG. 2B schematically illustrates an example of hardware architecture ofan acoustic processing device of the system of FIG. 1;

FIG. 3 schematically illustrates another example of hardwarearchitecture of a source device;

FIG. 4 schematically illustrates an algorithm for initialising thesource device;

FIG. 5 schematically illustrates an algorithm of nominal operating ofthe source device;

FIG. 6 schematically illustrates a simplified perspective view of ashell of a box in which the acoustic processing device may be installed;

FIG. 7A schematically illustrates a perspective view of a microphonesupport intended to be placed in the box;

FIG. 7B illustrates schematically another view of the microphonesupport.

In a system in which a reproduction device is intended to reproduce, inthe form of an audible signal, an audio signal supplied by sourceequipment, it is proposed to implement an initialisation phase in whicha propagation latency is determined between the emission of the audiosignal by the source equipment and the reception of a correspondingaudible signal by at least one microphone intended to capture at leastthe voice of a user in a nominal operating phase. A buffer is thenconfigured with a reading-triggering threshold defined according to thedetermined propagation latency. Then, in the nominal operating phase,when the equipment transmits an audio signal to the reproduction device,the equipment also transmits it to the buffer, which thus causes adelay. An acoustic processing unit adapted for delivering an audiosignal filtered by attenuation or suppression of a reference audiosignal from a received audio signal is used, with, as input, what iscaptured by the microphone or microphones and with, as reference signal,the signal delayed by the buffer.

FIG. 1 schematically illustrates a system in which the invention may beimplemented.

The system in FIG. 1 comprises an audio or audiovisual signal sourcedevice 103. According to a first example, the source device 103 is adigital decoder adapted for receiving and decoding audiovisual signalscoming from a satellite link or an Ethernet link to a home gateway viawhich audiovisual contents are received from the Internet. According toa second example, the source device 103 is a Blu-Ray (registered trademark) reader or a computer on which a media player is executed. Anydevice adapted for supplying an audio signal intended to be reproducedby a sound reproduction device can be used.

The system of FIG. 1 further comprises a sound reproduction device 101,which may be an audiovisual reproduction device. According to a firstexample, the sound reproduction device 101 is a screen comprisingintegrated loudspeakers. According to a second example, the soundreproduction device 101 is a hi-fi amplifier.

The source device 103 comprises an interface 151 for being connected tothe sound reproduction device 101 by means of a link 141. The soundreproduction device 101 comprises an interface 110 for being connectedto the source device 103 via the link 141. For example, the link 141 isin accordance with the HDMI (High-Definition Multimedia Interface), WHDI(Wireless Home Digital Interface), SPDIF (Sony/Philips DigitalInterconnect Format) or Peritel (registered trade mark) specifications.Thus the sound reproduction device 101 is capable of reproducing anyaudio signal received from the source device 103 via the link 141.

The system of FIG. 1 further comprises an acoustic processing device 102and at least one microphone 111, 112. The acoustic processing device 102comprises at least one interface 121, 122 adapted for connecting themicrophone or microphones 111, 112. The acoustic processing device 102is thus able to receive audio signals corresponding to sound signalscaptured by the microphone or microphones 111, 112. The acousticprocessing device 102 also comprises an interface 123 for beingconnected to the source device 103 by means of a link 142. The sourcedevice 103 comprises an interface 153 for being connected to theacoustic processing device 102 via the link 142. For example, the link142 is in accordance with the HDMI, USB (Universal Serial Bus) or IEEE1394 specifications.

The microphone(s) 111, 112 enable(s) capturing a sound environment, andin particular the sound signals broadcast by the reproduction device 101and the voice of a user of the system.

The source device 103 and the acoustic processing device 102 may beincorporated in the same box and may further be implemented on a samePrinted Circuit Board (PCB), the link 142 then being a track of thePrinted Circuit Board.

FIG. 2A schematically illustrates an example of hardware architecture ofthe source device 103.

The source device 103 comprises an audio signal supplying unit 211 forsupplying an audio signal, for example resulting from a demultiplexingand decoding of an audiovisual signal received via a satellite link. Theaudio signal is supplied to the interface 151 and to the input of abuffer 202 of the FIFO (First-In First-Out) type of the source device103. During an initialisation phase, the audio signal is also suppliedto a control unit 203 of the source device 103. During theinitialisation phase, another audio signal, coming from the interface153, is also supplied to the control unit 203.

The audio signal supplying unit 211 may further comprise a generatorgenerating an audio signal according to a predefined pattern, usableduring the initialisation phase.

The aforementioned initialisation phase is detailed hereafter inrelation to FIG. 4, and a subsequent phase of nominal operating of thesource device 103 is detailed hereafter in relation to FIG. 5.

The source device 103 comprises a processing unit 212 intended to applya processing to a filtered audio signal, coming from the interface 153.According to a first example, the processing unit 212 implements a voicerecognition mechanism. According to a second example the processing unit212 implements a shaping mechanism for transmitting the filtered audiosignal in the context of a teleconference.

FIG. 2B illustrates schematically an example of hardware architecture ofthe acoustic processing device 102.

The acoustic processing device 102 comprises an acoustic processing unit201, the function of which is to suppress a first audio signal, referredto as reference signal, from a second audio signal. The reference audiosignal is supplied by the source device via the link 142. The secondaudio signal is the audio signal resulting from the sound signalcaptured by the microphone(s) 111, 112. The acoustic processing unit 201then supplies, to the source device 103 via the link 142, a filteredaudio signal, i.e. devoid as far as possible of the reference audiosignal, when this reference audio signal has been detected in the signalcaptured by the microphone(s). For example, the acoustic processing unit201 is a component with reference CX20708-21X from the companyConnexant.

It should be noted that the acoustic processing unit 201 may comprise aninternal buffer performing the processing operations expected by theacoustic processing unit 201. However, this internal buffer serves onlyto store the audio signals during a predefined time window, for examplearound 200 ms, so as to carry out these processing operations. Noreading-triggering threshold is associated therewith and cannot beconfigured.

FIGS. 2A and 2B are respectively complementary examples of hardwarearchitecture of the source device 103 and of the acoustic processingdevice 102. A different distribution of the functions implemented can beenvisaged. For example, the control unit 203 and/or the FIFO 202 can beimplemented in the acoustic processing device 102. The arrangementaccording to FIGS. 2A and 2B does however have the advantage of allowingeasy update of devices supplying audio or audiovisual contents alreadydeployed, for example in private households. This is because, taking theexample of satellite decoders or of television over IP (InternetProtocol), these implement numerous functions by software. It is theneasy to upgrade this software in order to implement the functionsdescribed herein in relation to the source device 103. It would then besufficient to add thereto the acoustic processing device 102 in order toimplement the invention, without having to replace the hardware platformof these decoders.

The term “equipment” will be used to designate either a device or a setof devices implementing these functions.

FIG. 3 schematically illustrates another example of hardwarearchitecture of the source device 103, which then comprises, connectedby a communication bus 310: a processor or CPU (Central Processing Unit)300; a random access memory RAM 301; a read-only memory 302, a storageunit or a storage-medium reader, such as a Hard Disk Drive HDD 303; afirst interface 304 for communicating via the link 141; and a secondinterface 305 for communicating via the link 142.

It should be noted that the acoustic processing device 102 can beimplemented with a similar hardware architecture.

In the context of the architecture presented in FIG. 3, the FIFO 202 canbe implemented within the second interface 305 or within the RAM 301,for example in the form of a concatenated list.

The processor 300 is capable of executing instructions loaded into theRAM 301 from the ROM 302, from an external memory (not shown), from astorage medium such as the hard disk drive HDD 303, or from acommunications network. When the source device 103 is powered up, theprocessor 300 is capable of reading instructions from the RAM 301 andexecuting them. These instructions form a computer program causing theimplementation, by the processor 300, of all or some of the algorithmsand steps described hereafter. All or some of the algorithms and stepsdescribed hereafter can be implemented in software form by the executionof a set of instructions by a programmable machine, such as a DSP(Digital Signal Processor) or a microcontroller, or be implemented inhardware form by a machine or a dedicated component, such as an FPGA(Field-Programmable Gate Array) or an ASIC (Application-SpecificIntegrated circuit).

FIG. 4 schematically illustrates an algorithm implementing aninitialisation phase 400 of the source device 103.

In a step 401, the source device 103 sends an audio signal via theinterface 151. This audio signal preferably corresponds to a predefinedpattern. This audio signal may also a priori be unknown to the sourcedevice 103, for example resulting from a demultiplexing and decoding ofan audiovisual signal received by the source device 103 via a satellitelink. In the architecture presented in FIG. 2A, the source device 103also sends the audio signal to the control unit 203.

In a following step 402, the source device 103 determines informationrepresentative of an instant at which the source device 103 has sent theaudio signal via the interface 151. The audio signal sent by the sourcedevice 103 is therefore intended to be reproduced by the reproductiondevice 101. The reproduction device 101 decodes the audio signaltransmitted by the source device 103 and generates a corresponding soundsignal, the microphone(s) 111, 112 being adapted for capturing thissound signal.

In a following step 403, the source device 103 performs, or requests, asound-environment capture. To do so, the source device 103 instructs theacoustic processing device 102, via the link 142, to start asound-environment capture thanks to the microphone(s) 111, 112. Duringthis initialisation phase, the source device 103 does not transmit anyreference audio signal to the acoustic processing device 102 via theinterface 153. The acoustic processing device 102 then retransmitsdirectly to the source device 103 the audio signal corresponding to thesound signal captured by the microphone(s) 111, 112, no reference audiosignal having to be suppressed from the sound signal captured by themicrophone(s) 111, 112. In the architecture presented in FIG. 2A, thesource device 103 sends the audio signal received from the acousticprocessing device 102 to the control unit 203.

In a following step 404, the source device 103 determines informationrepresentative of an instant at which the acoustic processing device 102has received the audio signal thanks to the microphone(s) 111, 112. Itcan be considered that the instant at which the acoustic processingdevice 102 has received the audio signal thanks to the microphone(s)111, 112 is the same as that at which the source device 103 has receivedthe audio signal via the interface 153. It is then considered that theprocessing operations performed by the acoustic processing device 102have negligible latency. If such is not the case, the source device 103has, by configuration, knowledge of this latency and can thus take itinto account.

In order to determine the instant at which the acoustic processingdevice 102 received the audio signal thanks to the microphone(s) 111,112, the source device 103 detects an instant at which the audio signalreceived by the interface 153 is above a predefined threshold. Thesource device 103 then considers that this instant of crossing saidpredefined threshold is the one at which the acoustic processing device102 received the audio signal thanks to the microphone(s) 111, 112.According to a variant embodiment, the source device 103 makes acorrelation between the audio signal sent via the interface 151 and theaudio signal received via the interface 153, in order to determine towhich time window the audio signal sent corresponds in the receivedaudio signal. To do so, a matched filter, also referred to as Northfilter, can be applied. The use of such a filter advantageouslymaximises the signal to noise ratio. Other correlation methods may beused.

In a following step 405, the source device 103 determines informationrepresentative of a propagation latency, which is the difference betweenthe instant at which the acoustic processing device 102 received theaudio signal thanks to the microphone(s) 111, 112 and the instant atwhich the source device 103 sent the audio signal via the interface 151.This propagation latency is determined thanks to the informationdetermined in steps 404 and 402 respectively.

In a following step 406, the source device 103 determines informationrepresentative of a triggering threshold of the FIFO 202, to beimplemented during the nominal operating phase of the source device 103.This triggering threshold of the FIFO 202 is determined according to thepropagation latency determined at the step 405, and enables applying adelay to the reference audio signal to be transmitted to the acousticprocessing device 102 via the interface 153. If the propagation timebetween the source device 103 and the acoustic processing device 102 isneglected, this delay is equal to the propagation latency determined atthe step 405. Otherwise this delay is equal to the propagation latencydetermined at the step 405 from which a predefined value of thepropagation time between the source device 103 and acoustic processingdevice 102 is subtracted.

Then, the source device 103 configures the FIFO 202 so that, in thenominal operating phase, the triggering threshold determined at the step405 is applied. The initialisation phase is then ended and the nominaloperating phase can begin.

The source device 103 may supply to the user an indication that theinitialisation phase is under way, for example by means of an LED (LightEmitting Diode) of a user interface. This can enable the user to knowwhether he must limit any ambient noise in order to facilitate thedetection of the audio signal expected in return by the source device103.

In the architecture presented in FIG. 2A, the steps 402, 404, 405 and406 are performed by the control unit 203.

FIG. 5 schematically illustrates an algorithm of nominal operating ofthe source device 103, once the initialisation phase has been executed.

In a step 501, the source device 103 activates the filling of the FIFO202. No data item is then present in the FIFO 202.

In a following step 502, the source device 103 activates the soundsignal capture thanks to the microphone(s) 111, 112. To do this, thesource device 103 sends to the acoustic processing device 102 aninstruction to trigger such a capture. An audio signal corresponding tothe sound signal captured by the microphone(s) 111, 112 is then receivedby the acoustic processing unit 201.

In a following step 503, the source device 103 activates the sending ofan audio signal to the reproduction device 101 via the interface 151.This audio signal results for example from a demultiplexing and decodingof an audiovisual content received or read by the source device 103. Thesource device 103 having activated the filling of the FIFO 202, theaudio signal is also stored in the FIFO 202.

In a following step 504, the source device 103 checks whether thefilling threshold of the FIFO 202 determined at the step 406 is reached.If such is the case, a step 505 is performed; otherwise the step 504 isreiterated.

In the step 505, the source device 103 activates the reading of the FIFO202. The data stored in the FIFO 202 are then transmitted as a referenceaudio signal to the acoustic processing device 102 via the interface153. This reading of the FIFO 202 takes place at the rate at which thedata of the audio signal are written in the FIFO 202. A time delay, theduration of which is adapted so as to compensate for the propagationlatency determined at the step 405, is thus applied to the audio signalsupplied by the source device 103 to the acoustic processing device 102.

Thus, thanks to the application of this delay, the audio signals inputto the acoustic processing unit 201 are sufficiently synchronised toenable the acoustic processing unit 202 to suppress the reference audiosignal from the audio signal corresponding to the sound signal capturedby the microphone(s) 111, 112. In this way, the audio signal supplied tothe processing unit 212 is filtered and substantially devoid of thesound signal corresponding to the audio signal reproduced by thereproduction device 101. A slight noise may however remain through thedistortions in the sound signal captured by the microphone(s) 111, 112with respect to the reference audio signal. Then, when the user wishesto use voice commands or participate in a teleconference, his voice canbe clearly distinguished in the audio signal, even if the sound volumeof the reproduction device 101 is high.

FIG. 6 schematically illustrates a simplified perspective view of ashell of a box 600 in which the acoustic processing device 102 may beinstalled.

The shell of the box 600 comprises a first part 601 and a second part602. The two parts 601 and 602 are intended to be connected to eachother, for example by adhesive bonding, or by means of assembly screws,or using clips.

Preferably, said first part 601 serves as a cover for said second part602. The external thickness of this first part is shown in broken linesin FIG. 6. The acoustic processing device 102 consists of an electronicboard on which components fulfilling the previously described functionsare mounted. The electronic board is mounted on the internal face ofsaid first part 601. The electronic board may be assembled with saidfirst part 601 by means of assembly screws, rivets or clips.

The microphones 111, 112 are also integrated in the box 600, the shellof which comprises, for each microphone 111, 112, a first slot 610 and asecond slot 611. These slots 610, 611 enable the microphones 111, 112 tocapture the sound environment, as described hereafter in relation toFIGS. 7A and 7B. In the illustration in FIG. 6, the slots 610, 611 areformed in said second part 602 of the shell.

FIG. 7A schematically illustrates a perspective view of a microphonesupport 701 intended to be placed in the box 600. Each microphone 111,112 is then unidirectional and has an associated support 701.

The support 701 intended to receive the microphone 111 or 112 in anadjusted manner is preferably manufactured from rubber, so as to isolatethe microphone 111 or 112 from vibrations transmitted by mechanicalparts of the box 600. Microphones with the referenceCM1045RFH-35BL-C56F1K-LF from the company MWM Acoustics are for exampleused.

On one face of the support 701, two slots 710, 711 are formed, intendedto be respectively placed so as to match the slots 610, 611 formed inthe shell of the box 600, when the support 701 is installed in the box600.

The support 701 has a cavity 702 emerging on the slots 710, 711, andintended to receive the microphone 111 or 112. Once installed in thecavity 702, the microphone 111 or 112 is disposed so that a face of themicrophone 111 or 112 in the direction of the sound signal to befavoured is inline with the slot 711 and therefore with the slot 611;furthermore, the microphone 111 or 112 is disposed so that the face ofthe microphone 111 or 112 opposite to the direction of the sound signalto be favoured is inline with the slot 710 and therefore the slot 610.In typical designs of unidirectional microphones this face opposite tothe direction of the sound signal to be favoured comprises a hole thatenables the sounds other than those to be favoured to enter through therear, i.e. those that come from directions other than the one from whichthe sound signal to be favoured comes. In other words, this holeattenuates the ambient noise without eliminating it. To do so, it ishowever necessary for the propagation times of the sound signal from theslots made in the shell of the box 600 and the aforementioned two facesof the microphone 111, 112 to be substantially identical, i.e. for thedistances between these slots and these faces to be substantiallyidentical. The arrangement of the support 701 enables achieving thisobjective. The term “substantially” means that any difference existingis negligible with regard to the reactivity of the microphone.

The combination of the support 701 as presented and at least onemicrophone 111, 112 thus enables highlighting the sound signal (thevoice of the user in the system of FIG. 1) in the direction favoured bythe unidirectional microphone(s) 111, 112. “Highlighting” means bringingout the voice of the user with respect to the other sounds in the soundenvironment. This facilitates the processing carried out by the acousticprocessing device 102.

FIG. 7B schematically illustrates another view of the microphone support701. It is clear, more prominently in this view, that the slot 711 ispreferably formed by a step, or recess. The slot 711 is thusdefinitively formed when the support 701 is mounted in abutment on theinternal face of the first part 601 of the shell of the box 600.

It should be noted that the support 701 can be used to install aunidirectional microphone in a box without implementing the processingoperations implemented by the source 103 and acoustic processing 102devices. This enables improving the prominence of the voice of the user.

The invention claimed is:
 1. Equipment comprising a first interfaceintended to be connected to a sound reproduction device and at least onesecond interface intended to be connected to at least one microphone,said equipment comprising an acoustic processing unit adapted fordelivering an audio signal filtered by attenuation or suppression of areference audio signal from an audio signal received via said secondinterface, wherein said equipment is configured for implementing aninitialisation phase comprising: determining a propagation latencybetween an instant of transmission of a first audio signal via saidinterface and an instant of reception of a second audio signal via saidsecond interface; and configuring a buffer with a reading-triggeringthreshold defined according to said determined propagation latency,wherein said equipment is further configured for implementing a nominaloperating phase comprising: transmitting a third audio signal via saidfirst interface, the reference signal used by the acoustic processingunit resulting from a passage of the third audio signal through saidbuffer.
 2. The equipment according to claim 1, wherein said first audiosignal consists of a predefined pattern.
 3. The equipment according toclaim 1, wherein determining the propagation latency comprises detectinga crossing of an amplitude threshold of said second audio signal.
 4. Theequipment according to claim 1, wherein determining the propagationlatency comprises applying a North filter between said first audiosignal and said second audio signal.
 5. The equipment according to claim1, wherein the initialisation phase is implemented in a control unitconnected to an output of the acoustic processing unit for receivingsaid filtered audio signal, and wherein the control unit is configuredfor deacticating any transmission of reference audio signal to saidacoustic processing unit during said initialisation phase.
 6. Theequipment according to claim 1, wherein a first device implements theinitialisation phase and said first interface, and is configured fortransmitting the third audio signal, and wherein the acoustic processingunit and said second interface are implemented in a second deviceintended to be connected to said first device.
 7. The equipmentaccording to claim 1, wherein, said microphone(s) being unidirectional,the acoustic processing unit and said microphone(s) are implemented in abox comprising, for each microphone, a first slot and a second slot, andwherein each microphone is installed in a cavity of a support in which afirst slot and a second slot are also formed, and placed so as tocorrespond respectively to said slots in the box when said support ismounted in said box, wherein said support is adapted so that thedistances between said first slots and a face of said microphone placedin the direction of a sound signal to be favoured and the distancesbetween said second slot and an opposite face of said microphone aresubstantially identical.
 8. A method implemented by equipment comprisinga first interface connected to a sound reproduction device and at leastone second interface connected to at least one microphone, saidequipment comprising an acoustic processing unit adapted for deliveringan audio signal filtered by attenuation or suppression of a referenceaudio signal from an audio signal received via said second interface,wherein said method comprises an initialisation phase comprising:determining a propagation latency between an instant of transmitting afirst audio signal via said first interface and an instant of receptionof a second audio signal via said second interface; and configuring abuffer with a reading-triggering threshold defined according to saiddetermined propagation latency, wherein the method further comprises anominal operating phase comprising: transmitting a third audio signalvia said first interface, the reference signal used by the acousticprocessing unit resulting from a passage of the third audio signalthrough said buffer.
 9. Non-transitory storage medium storing a computerprogram comprising instructions for implementing, by equipment, themethod according to claim 8, when said program is executed by aprocessor of said equipment.